1. Field of the Invention
The present invention relates to improving the properties of particular molding compositions, particularly those comprising polyphenylene oxides (also known as polyphenylene ethers) and a polyester through the use of a phosphoroustrislactam as a compatibilizing agent.
2. Description of the Prior Art
Engineered plastics enjoy widespread popularity for the production of articles through the use of molding or casting processes. These engineering plastics are frequently blends of two or more specific constituents which feature specific properties, i.e., toughness, rigidity, chemical resistance, long-term hygrothermal dimensional stability, dielectric strength, and the like. While such engineering plastics comprising two or more specific constituents would optimally exhibit the beneficial properties of each constituent, unfortunately, as is well known to the art, the formation of blended polymeric materials are rarely attained which offer these desirable characteristics of the constituents making up its composition, without simultaneously suffering from some detrimental quality.
Poly(alkylene terepthalates) including poly(ethylene terepthalate), also known to the art by its acronym "PET", and poly(butylene terepthalate), similarly referred to as "PBT" are aromatic polyesters which enjoy frequent use where rigidity, ductility, high melting point and solvent resistance, are required. This is known to the art to be due to the relatively high degree of crystallinity which polyalkylene terephthalates, particularly PBT, exhibit subsequent to cooling from the melt. However, these materials are known have relatively low glass transition temperatures, "T.sub.g " and suffer heat distortion under mechanical loads at relatively low temperatures. Further, these materials are also known to suffer from a marked loss in their impact resistance subsequent to annealing or heat ageing, which may be due to subsequent processing of the article during its production, or from prolonged exposure to heat during its use. Blends of poly(phenylene ethers), which are also known to the art as poly(phenylene oxides) and which are commonly referred to as "PPE" or "PPO", and polyesters are expected to have increased heat distorion temperatures due to the high glass transition temperature, (interchangeably referred to as T.sub.g) of the PPE.
Polyphenylene ethers, also interchangeably referred to in the art as "polyphenylene oxides" are compounds known to exhibit good performance characteristics in elevated temperatures, or after heat ageing due to the high glass transition temperatures, T.sub.g which such materials typically exhibit. Further, such materials also exhibit good ductility and hydrolytic stability. Compositions comprising PPE and polyesters have been synthesized, and such compositions are described in PCT Application PCT/US/01027 for "Polyphenylene Ether-Polyester Copolymers, Precursors Therefor, Compositions Containing Said Copolymers, And Methods For Their Preparation" which describes a series of functionalizing agents, preferably those selected from among; maleic acid and derivatives thereof, fumaric acid and trimellitic anhydride, which are useful in promoting bonding between the PPE phase and polyester phase in the composition.
A further composition is that described in International Application PCT/US86/01572 for "Solvent-Resistant, Compatible Blends of Polyphenylene Ethers and Linear Polyesters" which describes compatibilized blends which include polyphenylene ether, polystyrene, poly(alkylene dicarboxylate), an elastomereic impact modifier and a further polymer.
A further composition comprising PPE, and a thermoplastic polyester blend containing a large proportion of polycarbonates which is compatibilized through the use of a poly(phenylene) ether is described in U.S. Pat. No. 4,927,881 issued on May 22, 1990.
A still further composition is that described in an application by the same inventors as in the instant application for a U.S. Patent titled "Process for Preparing Graft and Block Copolymers of Polyphenylene Oxides and Polyesters and Copolymers Prepared by said Process" filed on Dec. 4, 1989 and assigned Ser. No. 446,512. Therein is described a composition where a tris(phenyl)phosphite is used as a compatabilizing agent for polyphenylene oxide and polyester resins.
Such methods provide useful molding compositions having good physical properties, but also undesirably produce free phenol during the reaction which is widely regarded as a toxin and requires particular care in order to effect its removal.
The activity in this art, is merely one indication that there remains a need for continued development, and further improved compositions comprising PPE and polyesters. It is to this need, as well as other needs, that the present invention is addressed.